Length of Day

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Length of Day

 

the interval of time between sunrise and sunset, during which the sun is above the horizon. The length of day depends upon the geographic latitude of a place and upon the inclination of the sun. At the equator, the length of day is constant and equals 12 hours. In the northern hemisphere, the length of day is more than 12 hours during the positive inclination of the sun (that is, in the spring and summer) and less than 12 hours during the negative inclination of the sun (in the autumn and winter). At the equinoxes (spring and autumn), the day equals the night (if one does not consider refraction) everywhere on the earth. The longest day is the summer solstice and the shortest is the winter solstice. Within the polar circles, the length of day in the summer can exceed 24 hours (the polar day), and at the poles daytime lasts six months.

References in periodicals archive ?
Compare this to hibernation's triggers, day length and hormones.
Over the sampling period of four years, mean shell growth was significantly correlated with day length (correlation coefficient 0.
The research predicts the dates of leaf and flower emergence based on day length, and suggests spring will arrive a median of three weeks earlier over the next century.
The new study, published in the July 11 Nature, found trends in day length after subtracting the influence of weather, allowing researchers to home in on the effect of Earth's fluid core.
n=179&month=3&year=2013&obj=sun&afl=-11&day=1) in New York City , this past Sunday had a day length of 12 hours, one minute and eight seconds; when the equinox arrives, the day will be 12 hours, nine minutes and 18 seconds long.
It has long been known that plants use an internal time-keeping mechanism known as the circadian clock to measure changes in day length.
Australia is a particularly good place for this type of study as it spans nearly 3000 miles from north to south, with a large variation in climate, day length and sun strength -- from Queensland in the north to Tasmania in the south.
Material is in chapters on climate and day length, plant propagation, field preparation and plant care, field planting, harvesting and postharvest, and marketing and economics.
Professor David Hazlerigg from Aberdeen University said: "Understanding this process is vital as seasonal changes in day length are used by animals to synchronise major life-history events such as migration, moulting, and reproduction.
Poinsettias are photoperiodic which means flowering is initiated by a change in day length.
Having developed the NAM population, Holland, Buckler, and their colleagues are now taking a closer look at some of the genes that control flowering time and a related characteristic known as "photoperiod sensitivity," or sensitivity to day length.